Electron discharge device of the cavity resonator type with feedback



.J. J. LlVlNgOOD ETAL July 31, 1951 2,562,319

ELECTRON DISCHARGE EVICE OF THE CAVITY RESONATOR TYPE WITH FEEDBACK Filed Feb. 18, 1946 INVENTORS JQHN J. LIVINGOOD WINFQELD W. SALISBURY EDWARD S. WELGH ATTORNEY Patented July 31, 1951 ELECTRON DISCHARGEDE-VICE OF THE CAVITY RESONATORL TYPE "WITH FEEDBACK John J. Livingood and WinfieldAW. Salisb'ury,.

Cedar Rapid'slo'wa, and} Edward S. Welch; Cambridge, Mass, assignorsto the" United States i.v America as representedby the Secretary of War Application February18, 19.4.6, Serial No.648,542.

4 Claims.

This invention, relates to, an, electronic device, and, more particularly, to vacuum, tubesof the resnatron type. I

It is at present known to obtainthe necessary feedback in an oscillating resnatronby the provision .of one or more cathode supported conductors, wires, or.,rods that extend radially outwardly fromthe cathode structure. of the tube through the controland the screen grids toward theanode structure, with the outerextremities of:the r0ds or. wiresjin spaced relation to the anode. Such wires couple .the cathode-control grid cavity and thescreen grid-anode cavity of r the resnatron. Heretofore, the wires wouldhave-been'of molybdenum, preferably soldered into athreaded piece of copper rod screwed into a tapped drilling; in the cathode structure, adjacent one-end of thefilament thereof. This practice, ha been-found to possess a number of disadvantages. The proper length of feedback-wire is found by experimentaw tion. The feedback; capacity between .the wire and the anode cannot bealtered .or varied with;- out' at least partially dismantlingthe-resnatron, and changing the-lengthofthe Wire or wires. The optimum length of the 'Wireis not quite the same for-the diiferent frequency adjustment of the resnatron, because-the position of the feedback capacitors shifts Withrespect tov the standing waves of voltage along the-resnatron as the wavelength is-altered. The-arrangement is poor, also, from a maintenance standpoint-because, to

change the cathode, the cathode, control grid.

and screen grid must be withdrawn from: the tube structure so that the feedback wireorwiresmay beremoved before the cathode can be withdrawn from within the, control grid; and because, oc+ casionally, thethreaded copper piecesmelt under the high temperature, present within the tube, and become'welded into the-drillings in the cathode-structure. Should the latter be thecase, it becomes necessary, then, to break off .one or more of" the molybdenum wires before-the cathode can be completely isolated from the grids.

An object ,of a this invention is .to improve the structureof .a resnatron'toobviateand to minimize the referred-todifficulties, and to provide the desired feedback in a resnatron in-a novel and more advantageou manner.

A featureof this invention comprises therprovision, of variable or adjustable feedbackmeans in aresnatron.

Another featurecomprises theprovision in a resnatron ofcapacitive feedback means supported from .or on the anode of the device.-

Still another. feature-comprises incorporating feedback; means in'a-resnatron in the form-of one 7 or more conductors, wires orrods supported outside of the cathodestructure but extending inwardly toward the cathode structure. I

A further feature comprises feedback means within the resnatron; adjustable externally of the resnatron for varying ,the feedback, Withoutdis mantling the resnatron or after the resnatron hasbeen assembled, or during-operation of the resnatron.

An additional feature, comprise the addition of .a suitable shield or other protective means "on the cathode structureto guard against high potential arc-overs when inwardly extending'feedbackconductors, Wiresor rods are incorporated in the resnatron structure.

Still other objects "and features of theinvention, together with their attendant advantageous aspects, willbe obvious from the-general and the specific. description which follow hereinafter.

' Inyaccordancewith the invention, capacitive feedback between the cathode-control grid cavity andethescreen grid-anode cavity of a resnatron is incorporatedin a tube of that-type by'the provision of'oneor moreconductors, rodsorwires supportedfrom or electrically connected with the anode, that extend radially inwardly; from the outerwall of 'the'resnatron through the screen grid,and the control grid of the device, toward thecathode structure, the wireor wires being at its .,-or their inner ends'in, spaced relationto the cathode structure. The wire'or Wires are preferably ofi good'electrical .and thermo conducting material, for example, solid copper rod; each mounted at the inner end of water or other fluidcoolingtubing that extends from the outside of the.,resnatron through suitable vacuum sealing joints or means in the wall ofthe resnatron-along radi'alilines, The tubinggand, therefore, its 'assoc'iatedv wire, may be adjusted slidably' toand from thecathodestructure from outside of the resnatron. Toprotect the cathode structure, and particularly thin walled members, such as a Sylphon, that maybe associated with the cathode structure, against high potential arc-overs from the feedback rod or rods during testing or the operation of the device, asuitably proportioned small sheet or disk of metal, for example, copper, may bemounted on the cathode structure, ex,- tending parallel to the'cathode-structures axis and, to the Sylphon, oppositely disposed with reference to and spaced from the innermostend ofthe;feedback'rod,, the rod andthe disk together forming an adjustablejcapaciton or more" of theseadjustable feedback. rods are If. two

utilized, they may be spaced at equidistant posi tions along radial paths in the resnatron. To permit a maximum cooling of the feedback rod or wire, it may be preferred to shorten the wire or rod to the utmost so that, in such an arrangement, the movable element of the adjustable capacitor might constitute a thin plate or stub at the inner end of the tubing. Obviously, with the arrangement just described, the amount of capacitive feedback may be adjusted from outside the resnatron, eliminating the necessity to dis mantle the device, permitting ready experimentation to ascertain the appropriate spacing of the feedback rod from the cathode structure in order to provide the needed or the desired change in capacity, and eliminating the other referred-to difficulties present when the feedback rods are supported from the cathode structure.

A more complete understanding of the invention will be derived, it is believed, from the detailed description that follows, read with reference to the appended drawing, wherein:

Fig. 1 is a cross-sectional view of a portion of a resnatron illustrating the manner in which the invention may be embodied in such a device;

Fig. 2 is a plan view of the device of Fig. 1, taken along the line 22 thereof; and

Fig. 3 is an enlarged cross-sectional view of a portion of the device of Fig. 1, taken along the line 3% thereof, in order to show in detail the construction and relationship of the parts of the adjustable feedback means for a resnatron in accordance with this invention.

With reference to the drawings, there is shown so much of the structure of a resnatron as necessary for an understanding of this invention. The resnatrons outer walls comprise substantially cylindrical metallic sections l2, l4 secured firmly together by a plurality of fastening devices l6 and clampin therebetween, the anode structure N3 of the resnatron, and a feedback rod supporting member or annulus 2B which may be, for example, of brass. The adjacent surfaces of the sections 12, I4, the anode l8, and the member 2%] are vacuum sealed by means of sealing gaskets 22 which may be, for example, of rubber, and maintained in electrical contact by electrically conductive gaskets 24, which may be, for example, of tin. The electrode structure of the resnatron in accordance with known practice may comprise a cathode-control grid cavity 26 including cathode structure 28 and control grid 39 and a screen grid-anode cavity 32 including the anode structure and the screen grid 34. The cathode structure may include a Sylphon 36 and a plurality of filaments 38, and the control grid may contain a plurality of slots or apertures 40, each of which is located opposite a cathode filament to provide passage for electrons emitted from the cathode filaments. One or more openings 42 may be provided in the control grid for the passage through the control grid of one or more feedback conductors as will be described more fully further on.

The screen grid 34 may comprise a plurality of lengths of metallic tubing, for example, of copper, therebypermitting water, or other fluid, cooling of the screen grid. Variable capacitive feedback is provided by a fixed Or stationary disk, sheet or plate 4 5, secured to the cathode structure adjacent one end of the cathode filaments, and a radially adjustable, conductor, wire, or rod 4-5, three sets of which are shown spaced 'at approximately 120. The disk protects or guards the thin-walled Sylphon against being punctured, and thereby letting fluid, for example, water, from the Sylphon into the highly evacuated cavities, by possible high potential arcovers from the rod 46 during the operation of the resnatron. The enlarged cross-sectional view of Fig. 3 shows the adjustable variable feedback means in greater detail.

It comprises the rod 46 mounted on and closing one end of the outer tube 48 of a pair of coaxial tubes 48, 50, which may be of copper tubing, adapted to be coupled at their open and outer ends 52, 54 to a source (not shown) of cooling fluid, for example, water. The coaxial tubes 48, 50 are slidable as a unit to and fro within a central aperture 56 in a guide and stop plate 58, a central aperture 6|! of a vacuum seal 01' joint 62, and the multi-spring fingered end 64 of a metallic tube 66. The tube 66 threads into a radial tapped drilling 68 in member 20. The seal 62 may comprise the double flanged disk 10, the flange 12 making a soldered joint with the member 20, and the flange 74 being engaged b the L-sectioned clamp 16 that secures, the sealing gasket 18, which may be of rubber, in place. The plate 58 is supported from the disk 1!] by suitable spacers 8B and fastening devices 82, and limits the maximum inward movement of the feedback rod. In a specific embodiment constructed in accordance with the invention, the rod 48 was of the order of one-eighth inch diameter; the tubes 48, 5B of the order of fivesixteenths inch and one-eighth inch diameter, respectively; and tube 66, of the order of onehalf inch diameter. If it should be ecessary to cut away one or more tubes comprising the screen grid to permit passage of the feedback rod, obviously connecting pieces of screen grid tubing may be employed to provide continuous paths through the screen grid tubing for flow of cooling fluid therein. The opening in the screen grid for the feedback rodshould be made of sufficient size to reduce the direct capacity from the anode to the screen grid that the feedback rod or rods provide.

The cathode-grid cavity of an oscillatin resnatron must be excited by a fraction of the output voltage generated in the screen-anode cavity. When capacitive feedback is used, the feedback capacitor and the impedance of the cathode-grid circuit are connected in series across the output voltage in order to form a potential divider such that voltage of the proper magnitude and phase is impressed across the cathode-grid circuit. In this invention, the capacitance exists between the cathode structure and the rod which is connected to or supported on the anode; thus the cathode-grid and the anodescreen cavities are connected as required.

Although the invention has been described with reference to a specific structural embodiment, it is obviously not limited thereto and the illustrative structures, proportions, and materials may be varied without departin from the spirit of the invention, the scope of which is evidenced by the prior art and appended claims.

What is claimed is:

1. An electron discharge device of the resnatron type comprising cylindrical cathode control grid, screen grid, and anode electrodes mounted concentrically in the order mentioned with said anode electrode surrounding the other electrodes, an input cavity resonator coupled between said cathode and control grid electrodes, an output cavity resonator coupled between said anode and screen grid electrodes, a conductive trol grid, screen grid, and anode electrodes mounted concentrically in the order mentioned I with said anode electrode surrounding the other electrodes, an input cavity resonator coupled be tween said cathode and control grid electrodes, an output cavity resonator coupled between said anode and screen grid electrodes, a conductive feedback probe extending radially into said input resonator, said probe being capacitively coupled to said input resonator, and means for adjusting the position of said feedback probe during operation of said discharge device, said adjusting means including electrically conductive gaskets mounting and sealing said feedback probe through said anode electrode and electrically connecting said feedback probe and said anode electrode, and means located outside said anode electrode for moving said feedback probe with respect to said anode electrode over said gaskets.

3. An electron discharge device of the resnatron type comprising cylindrical cathode, control grid, screen grid, and anode electrodes mounted concentrically in the order mentioned with said'anode electrode surrounding the other electrodes, an input cavity resonator coupled between said cathode and control grid electrodes, an output cavity resonator coupled between said anode and screen grid electrodes, a conductive feedback probe electrically and mechanically connected to said anode electrode and extending radially into said input resonator, said probe being capacitively coupled to said input resonator, and a conductive element mounted on said cathode electrode and positioned between said cathode electrode and said feedback probe for shielding said cathode from sparks from said feedback probe and providing capacitive coupling between said feedback probe and said cathode electrode.

4. An electron discharge device of the resnatron type comprising cylindrical cathode, control grid, screen grid, and anode electrodes mounted concentrically in the order mentioned with said anode electrode surrounding the other electrodes, an input cavity resonator coupled between said cathode and control grid electrodes, an output cavity resonator coupled between said anode and screen grid electrodes, a conductive feedback probe electrically and mechanically connec ted to said anode electrode and extending radially into said input resonator, said probe being capacitively coupled to said input resonator, the innermost end of said feedback probe being solid and the rest of said probe being hollow and constructed so as to facilitate circulation of a fluid therethrough, and fluid circulating means coupled to the outer end of said probe.

JOHN J. LIVINGOOD.

WINFIELD W. SALISBURY.

EDWARD S. WELCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,128,236 Dallenbach Aug. 30, 1938 2,157,952 Dallenbach May 9, 1939 2,284,405 McArthur May 26, 1942 2,287,845 Varian et a1 June 30, 1942 2,295,680 Mouromtseff et a1. Sept. 15, 1942 2,314,794 Linder Mar. 23, 1943 2,411,953 Brown Dec. 3, 1946 2,481,151 Powers Sept. 6. 1949 

